This invention relates to a plasma cutting and welding tip, and more specifically, to a counterbored plasma tip designed to prevent damage to the tip caused by plasma arc deflection.
Plasma arc cutting and welding is similar to other forms of arc cutting and welding in that an arc is arranged to run between an electrode in a torch and the workpiece that is to be cut. Generally, the electrode is at a negative polarity and the elections move to the workpiece, which is the anode. Considerable heat is generated in the arc and most of the heat is released at the anode.
The arc usually runs in an atmosphere of argon gas in order to prevent oxidation of the metal. Air is also a very common plasma gas and a Hafnium electrode is used particularly when cutting mild steels. In plasma welding or cutting, a tungsten electrode is used and inert gas, such as Argon flows through the torch. However, a narrow nozzle or tip is placed just below the electrode to constrict the arc thereby increasing the temperature of the arc as well as increasing the velocity of the inert plasma gas. Power used in plasma cutting is much higher than in conventional, or plasma arc welding and the arc is much more constricted by the plasma cutting tip. Therefore, the combination of the power intensity and the gas flow can push a hole right through the metal workpiece making a plasma arc quite useful as a cutting torch.
Traditional plasma tip drag cutting is done with the tip orifice in contact with the metal to be cut. However, if the tip is moved onto new metal faster than the arc can cut or remove metal, the arc is deflected. If the plasma arc cutting tip is constructed to maximize cut quality, that is, constructed to severely constrict the outflow of the plasma arc, there is minimal tolerance for arc deflection in the tip and the arc is deflected into contact with the tip thereby causing tip damage or tip failure. One solution is to use a tip with an oversize orifice so that the arc is not constricted and so that the deflected arc does not touch the walls of the tip. However, this does not allow for optimum cutting efficiency because it does not constrict the arc so as to increase the force of the arc and the velocity of exiting plasma column.